The present invention relates to a four-wheel steer control system for a wheeled vehicle for improving a vehicle driving stability such as a straightahead running stability. II. Description of the Prior Art
A prior art steering control system of this kind is disclosed in the Japanese Provisional Patent Publication No. 60-161266 assigned to the same assignee of this application.
In the prior art steering control system, the control constants Kf, Kr, Tf and Tr are set to be constant irrespective of the steer angle .theta.. Due to this, when the steering wheel is slightly steered during straightahead running of the vehicle, a quick, sharp movement like a jerk of the vehicle results. This movement gives the driver a strange feel which does not occur in the two-wheel steer vehicle and therefore causes an uncomfort and unease of the driver.